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Myosin X and Cytoskeletal Reorganization
Ikebe, Mitsuo,Sato, Osamu,Sakai, Tsuyoshi Korean Society of Microscopy 2018 Applied microscopy Vol.48 No.2
Myosin X is one of myosin superfamily members having unique cellular functions on cytoskeletal reorganization. One of the most important cellular functions of myosin X is to facilitate the formation of membrane protrusions. Since membrane protrusions are important factors for diverse cellular motile processes including cell migration, cell invasion, path-finding of the cells, intercellular communications and so on, it has been thought that myosin X plays an important role in various processes that involve cytoskeletal reorganization including cancer progression and development of neuronal diseases. Recent studies have revealed that the unique cellular function of myosin X is closely correlated with its unique structural characteristics and motor properties. Moreover, it is found that the molecular and cellular activities of myosin X are controlled by its specific binding partner. Since recent studies have revealed the presence of various specific binding partners of myosin X, it is anticipated that the structural, biochemical and cell biological understanding of the binding partner dependent regulation of myosin X function can uncover the role of myosin X in diverse cell biological processes and diseases.
도시녹지로서 옥상녹화의 다면적 기능 평가를 위한 기준에 관한 연구
Bo Hyun Kim,Konomi Ikebe,Hajime Koshmizu,Jie woong Lee 한국인간·식물·환경학회 2013 인간식물환경학회지 Vol.16 No.1
Green roof policies has helped to advance urban greening by creating green spaces on previously unused rooftops. However, there are no requirements covering matters such as greening methods, operation and maintenance obligations and many problems for sustainability and functioning of green roof and green space have been pointed out. This research is intended to clarify the contents and criteria of green roof policies currently implemented in Korea, Japan and other countries, compare them with the evaluation criteria for sustainable and public benefit rating systems and propose comprehensive indices for evaluating the multidimensional functions of green roof from the perspective of urban open space. As a result, it is found that obligation, grant, reimbursement, density bonus and tax credit are frequently used as green roof policies and 41 criteria including percentage of greening area, percentage of trees or shrubs, reduction of heat island effect, open space, landscape, and promotion of biodiversity are identified as criteria applicable to evaluating the multidimensional functions of green roof from the perspective of urban open space, respectively.
The tail binds to the head-neck domain, inhibiting ATPase activity of myosin VIIA.
Umeki, Nobuhisa,Jung, Hyun Suk,Watanabe, Shinya,Sakai, Tsuyoshi,Li, Xiang-dong,Ikebe, Reiko,Craig, Roger,Ikebe, Mitsuo National Academy of Sciences 2009 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.106 No.21
<P>Myosin VIIA is an unconventional myosin, responsible for human Usher syndrome type 1B, which causes hearing and visual loss. Here, we studied the molecular mechanism of regulation of myosin VIIA, which is currently unknown. Although it was originally thought that myosin VIIA is a dimeric myosin, our electron microscopic (EM) observations revealed that full-length Drosophila myosin VIIA (DM7A) is a monomer. Interestingly, the tail domain markedly inhibits the actin-activated ATPase activity of tailless DM7A at low Ca(2+) but not high Ca(2+). By examining various deletion constructs, we found that deletion of the distal IQ domain, the C-terminal region of the tail, and the N-terminal region of the tail abolishes the tail-induced inhibition of ATPase activity. Single-particle EM analysis of full-length DM7A at low Ca(2+) suggests that the tail folds back on to the head, where it contacts both the motor core domain and the neck domain, forming an inhibited conformation. We concluded that unconventional myosin that may be present a monomer in the cell can be regulated by intramolecular interaction of the tail with the head.</P>
Phospholipid-dependent regulation of the motor activity of myosin X
Umeki, Nobuhisa,Jung, Hyun Suk,Sakai, Tsuyoshi,Sato, Osamu,Ikebe, Reiko,Ikebe, Mitsuo Nature Publishing Group, a division of Macmillan P 2011 Nature structural & molecular biology Vol.18 No.7
Myosin X is involved in the reorganization of the actin cytoskeleton and protrusion of filopodia. Here we studied the molecular mechanism by which bovine myosin X is regulated. The globular tail domain inhibited the motor activity of myosin X in a Ca<SUP>2+</SUP>-independent manner. Structural analysis revealed that myosin X is monomeric and that the band 4.1-ezrin-radixin-moesin (FERM) and pleckstrin homology (PH) domains bind to the head intramolecularly, forming an inhibited conformation. Binding of phosphatidylinositol-3,4,5-triphosphate (PtdIns(3,4,5)P<SUB>3</SUB>) to the PH domain reversed the tail-induced inhibition and induced the formation of myosin X dimers. Consistently, disruption of the binding of PtdIns(3,4,5)P<SUB>3</SUB> attenuated the translocation of myosin X to filopodial tips in cells. We propose the following mechanism: first, the tail inhibits the motor activity of myosin X by intramolecular head-tail interactions to form the folded conformation; second, phospholipid binding reverses the inhibition and disrupts the folded conformation, which induces dimer formation, thereby activating the mechanical and cargo transporter activity of myosin X.
An, Byung Chull,Sakai, Tsuyoshi,Komaba, Shigeru,Kishi, Hiroko,Kobayashi, Sei,Kim, Jin Young,Ikebe, Reiko,Ikebe, Mistuo American Chemical Society 2014 Biochemistry Vol.53 No.49
<P/><P>Motor activity of myosin III is regulated by autophosphorylation. To investigate the role of the kinase activity on the transporter function of myosin IIIA (Myo3A), we identified the phosphorylation sites of kinase domain (KD), which is responsible for the regulation of kinase activity and thus motor function. Using mass spectrometry, we identified six phosphorylation sites in the KD, which are highly conserved among class III myosins and Ste20-related misshapen (Msn) kinases. Two predominant sites, Thr<SUP>184</SUP> and Thr<SUP>188</SUP>, in KD are important for phosphorylation of the KD as well as the motor domain, which regulates the affinity for actin. In the Caco2 cells, the full-length human Myo3A (hMyo3AFull) markedly enlarged the microvilli, although it did not show discrete localization within the microvilli. On the other hand, hMyo3AFull(T184A) and hMyo3AFull(T188A) both showed clear localization at the microvilli tips. Our results suggest that Myo3A induces large actin bundle formation to form microvilli, and phosphorylation of KD at Thr<SUP>184</SUP> and Thr<SUP>188</SUP> is critical for the kinase activity of Myo3A, and regulation of Myo3A translocation to the tip of microvilli. Retinal extracts potently dephosphorylate both KD and motor domain without IQ motifs (MDIQo), which was inhibited by okadaic acid (OA) with nanomolar range and by tautomycetin (TMC) with micromolar range. The results suggest that Myo3A phosphatase is protein phosphatase type 2A (PP2A). Supporting this result, recombinant PP2Ac potently dephosphorylates both KD and MDIQo. We propose that the phosphorylation–dephosphorylation mechanism plays an essential role in mediating the transport and actin bundle formation and stability functions of hMyo3A.</P>